Electromagnetic sensor for measuring electromagnetic properties of a fluid and/or a solid comprising a flexible substrate
An electromagnetic sensor for use in an apparatus for measuring electromagnetic properties of a fluid and/or a solid, the sensor comprising a substrate in the form of a plate, a plurality of first sensor elements on the substrate, the first sensor elements forming a first array of the first sensor elements on the substrate, a plurality of second sensor elements on the substrate, the second sensor elements forming a second array on the substrate, wherein the first and second arrays are regular arrays and are mutually aligned geometrically, a plurality of electrical connectors on the substrate, and a plurality of electrical terminals on the substrate, the electrical connectors electrically connecting the first and second sensor elements to electrical terminals, wherein the first sensor elements each comprise a first type of sensor selected from an inductive sensor, a capacitive sensor and a magnetic sensor and the second sensor elements each comprise a second type of sensor selected from an inductive sensor, a capacitive sensor and a magnetic sensor, wherein the first type of sensor and the second type of sensor are different.
1. An apparatus for measuring electromagnetic properties of a fluid and/or a solid, the apparatus comprising:
an electromagnetic sensor which comprises a substrate in the form of a plate which comprises at least one printed circuit board, a plurality of first sensor elements printed on the at least one printed circuit board, the first sensor elements forming a first array of the first sensor elements on the substrate, a plurality of second sensor elements printed on the at least one printed circuit board, the second sensor elements forming a second array on the substrate, wherein the first and second arrays are regular arrays and are mutually aligned geometrically, a plurality of electrical connectors on the substrate, and a plurality of electrical terminals on the substrate, the electrical connectors electrically connecting the first and second sensor elements to the electrical terminals, wherein the first sensor elements each comprise a first type of sensor selected from an inductive sensor, a capacitive sensor and a magnetic sensor and the second sensor elements each comprise a second type of sensor selected from an inductive sensor, a capacitive sensor and a magnetic sensor, wherein the first type of sensor and the second type of sensor are different, wherein the substrate is flexible and is flexed to form a closed or open ring respectively completely or partly surrounding a central axis, and the first and second arrays form a plurality of annular arrays of the first or second sensor elements surrounding the axis, wherein each annular array is formed from a row of the respective first or second sensor elements in the respective first and second arrays, and the annular arrays define a central measurement zone surrounded by the annular arrays, wherein each first sensor element is wholly surrounded, in the direction of a plane extending parallel to the substrate, by a respective second sensor element and the second sensor element wholly surrounds, in the direction of a plane extending parallel to the substrate, the respective first sensor element, wherein the second sensor element has an external peripheral edge and an internal peripheral edge defining a central cavity in which is located the respective first sensor element, and the first sensor element is located inwardly of the internal peripheral edge of the second sensor element and there is no overlap between the respective first and second sensor elements.
2. The apparatus according to claim 1 , wherein each of the first and second arrays is a rectangular array comprising at least one row of the respective first and second sensor elements and a plurality of columns of the respective first and second sensor elements and wherein one of the first array or second array is located on a central region of the substrate and the other of the second array or first array is located on mutually spaced side regions of the substrate which are on respective opposite sides of the central region of the substrate.
3. The apparatus according to claim 1 , further comprising a plurality of third sensor elements printed on a surface of the at least one printed circuit board, the third sensor elements forming a third array of the third sensor elements on the substrate, wherein the third sensor elements each comprise a third type of sensor selected from an inductive sensor, a capacitive sensor and a magnetic sensor, wherein the first, second and third types of sensor are different, wherein the electrical connectors connect the third sensor elements to the electrical terminals.
4. The apparatus according to claim 1 , further comprising a plurality of guard elements printed on a surface of the at least one printed circuit board, the guard elements forming a fourth array of the guard elements on the substrate, wherein the fourth array comprises two parallel outer rows of guard elements, wherein each outer row of guard elements extends along a respective opposite edge of the substrate, wherein each guard element comprises a coil or an electrode which is adapted, when electrically energized in use, to provide a screening electromagnetic field defining an extremity of a sensing zone of the electromagnetic sensor, wherein the electrical connectors interconnect the plurality of guard elements and connect the guard elements to the electrical terminals.
5. The apparatus according to claim 4 , wherein the fourth array further comprises at least one central row of guard elements, each central row extending along a respective central region of the substrate and parallel with the two outer rows of guard elements.
6. The apparatus according to claim 1 , wherein each inductive sensor comprises a coil of electrically conductive material which is wound about a central axis to form at least one turn, wherein the electrically conductive material is selected from copper, graphene, or carbon.
7. The apparatus according to claim 6 , wherein each turn is in a common plane so that the respective coil is planar and in a single layer of the inductive sensor.
8. The apparatus according to claim 6 , wherein the coil is non-planar and formed in 1 to 8 layers of the inductive sensor, each layer of the inductive sensor comprising at least one turn.
9. The apparatus according to claim 6 , wherein each turn is composed of four linear sections and the respective coil is rectangular in plan, wherein the rectangular coil has a width:length ratio of from 1:2 to 2:1.
10. The apparatus according to claim 1 , wherein each capacitive sensor comprises a central layer of dielectric material between opposite layers of electrically conductive material, wherein the electrically conductive material is selected from copper, graphene, or carbon.
11. The apparatus according to claim 1 , wherein the apparatus further comprises a plurality of guard elements printed on a surface of the at least one printed circuit board, the guard elements forming a fourth array of the guard elements on the substrate, wherein the fourth array comprises two parallel outer rows of guard elements, and, wherein the sequence further comprises an annular array of the guard elements at each end of the sequence.
12. The apparatus according to claim 11 , wherein the sequence further comprises an annular array of the guard elements at a center of the sequence and between the first and second annular arrays.